Gas cylinder attachment using a formed pin as orifice liner

ABSTRACT

A spirally-wound, formed pin used as an orifice liner in a gas operated firearm. The spirally-wound, hollow, spring steel pin is useful in locating the gas cylinder on the barrel for the brazing operation and improves the location accuracy of the gas cylinder due to spring pin expansion. The spring pin tends to act as a protective liner to lessen the erosive effects of the explosive gases on the braze joint connecting the gas cylinder to the barrel.

United States Patent Hutton et al.

GAS CYLINDER ATTACHMENT USING A FORMED PIN AS ORIFICE LINER Inventors:James Cameron Hutton; Merle Francis Carter, both of Mohawk; KennethCharles Rowlands, Utica, all of NY.

Remington Arms Company, Inc., Bridgeport, Conn.

Filed: Jan. 30, 1974 Appl. No; 437,854

Assignee:

US. Cl. 89/193; 89/191; 89/193 Int. Cl. F4ld 5/04 Field of Search 89/191R, 191 A, 192, 193

[56] References Cited UNITED STATES PATENTS 1,387,889 8/1921 Johnston89/193 [451 July 8,1975

l/l96l Hepperle 89/191 H1969 Beretta 89/191 A Primary ExaminerStephen C.Bentley Attorney, Agent, or Firm-John H. Lewis, .1r.; Nicholas Skovran[57] ABSTRACT A spirally-wound, formed pin used as an orifice liner in agas operated firearm. The spirally-wound, hollow, spring steel pin isuseful in locating the gas cylinder on the barrel for the brazingoperation and improves the location accuracy of the gas cylinder due tospring pin expansion. The spring pin tends to act as a protective linerto lessen the erosive effects of the explosive gases on the braze jointconnecting the gas cylinder to the barrel.

10 Claims, 8 Drawing Figures GAS CYLINDER ATTACHMENT USING A FORMED PINAS ORIFICE LINER This invention relates to a gas operated firearm wherehigh-pressure gas, produced by propellant combustion, is generallychanneled from the bore of the gun barrel via a passage or orifice to anattached device, e.g. a gas cylinder, whereby the gas is allowed toimpinge on areas of the firearm to provide various functions. e.g. forceand motion to the firearm action, recoil attenuation, etc. Moreparticularly, the invention relates to the use of a formed pin as anorifice liner to effect several important functions, which will bedescribed later. Still more particularly, the invention relates to theuse ofa hollow, spring steel pin to locate the gas cylinder on thebarrel for the brazing operation and which is spring-biased against thewalls of the orifice in the gun barrel and the gas cylinder to improvethe location accuracy of the gas cylinder due to spring pin expansion.

In many, if not most, of the currently produced gas operated sportingfirearms the gas cylinders of whatever type are attached to the gunbarrels with a braze joint using a silver solder" as the brazingmaterial. In this process, both parts are fluxed, held together with asilver solder preform sandwiched in between and heated to effect thebraze joint. To prevent movement of the gas cylinder relative to thebarrel, as the solder turns liquid, a locating pin is commonly used toalign a hole in the barrel with a hole in the gas cylinder. Alignment ofthe gas cylinder rotationally and longitudinally relative to the barrelis achieved within the accuracy of the pin and hole tolerances whileallowing the gas cylinder to move closer to the barrel, under a clampingforce, as the solder" preform melts.

Two problems may arise with this method of using a solid, cylindricalpin to locate the gas cylinder on the barrel during the brazingoperation and drilling the gas orifice passages elsewhere in theinterface braze joint. First, the accuracy of gas cylinder location islimited by the diametral fit between the locating pin and the blindholes in the gas cylinder and barrel. Second, the high velocity andpressure of the bore gas as it flows through the braze joint tends toerode the relatively soft braze mate rial, creating an undercut ringarea around the orifice hole. The presence of bore gas in this area,particularly if the braze joint is of poor quality, can cause asignificant separative force between the gas cylinder and barrelpossibly causing failure of the braze joint in tension. It should benoted that the joint strength can deteriorate rapidly, because not onlydoes the eroded area create an increase in separative force, but it alsodecreases the tensile area remaining in the joint interface.Fortunately, shotgun bore pressures at the orifice hole are low,generally under 5,000 psi, with acceptable rates of braze erosion. Brazejoint failures do occur. however.

In a currently produced semi-automatic rifle, the gas cylinderattachment is effected by utilizing a cylindrical pin to locate the gascylinder on the barrel during the brazing operation and then axiallydrilling the gas orifice passage through the locating pin after brazingis complete. This method of using the locating pin body to shield thebraze joint from the erosive effects of the gas is important inpreventing braze joint failure when high orifice pressures of 50,000 psior greater of present rifle cartridges is considered.

However, the latter method requires the post-braze drilling of theorifice hole and then externally sealing the orifice hole. This isaccomplished in a manner described below.

It is an object of this invention to provide an econonical and easilypositioned liner for a gas orifice hole in a firearm.

It is another object of this invention to provide a liner for a gasorifice hole in a firearm which tends to lessen the erosive effects ofthe explosive gases.

Still another object of the invention is to provide a liner for a gasorifice hole in a firearm which helps to accurately locate the gascylinder on the gun barrel.

It is still another object of the present invention to provide anoutwardly-biased formed pin to act as an orifice liner for a gasoperated firearm.

Other objects will be obvious after reading the specification in which:

FIG. I is a sectional view of a prior art shotgun barrel having a gascylinder brazed thereto.

FIG. 2 is a sectional view ofa prior art firearm having a barrel with agas cylinder attached thereto by a brazed joint which is partiallyeroded away.

FIG. 3 is a sectional view of a prior art firearm having a barrel and agas cylinder attached and a gas cylinder locating pin acting as a gasorifice liner.

FIG. 4 is a sectional view of a firearm incorporating the presentinvention.

FIG. 5 is a sketch showing an exaggerated view of the spring pinlocating the gas orifice where the barrel opening is larger than the gascylinder opening.

FIG. 6 is a sketch showing an exaggerated view of the spring pinlocating the gas orifice where the barrel opening is smaller than thegas cylinder opening.

FIG. 7 is a top view of a simple spring roll pin which is included inthe present invention.

FIG. 8 is a top view of a spirally-wound spring pin which is thepreferred form of the invention.

As mentioned above, the prior art is shown in FIGS. 1-3. FIG. 1 shows acurrently-produced shotgun having a barrel I0 to which a gas cylinder 12is attached by brazing 14. A locating pin I6 is used to align an opening18 in the barrel with opening 20 in the gas cylinder. After the gascylinder is assembled and brazed, a gas orifice 22 is drilled throughthe walls of the gun barrel and the gas assembly. As mentioned above,the rotational and longitudinal alignment depends on the accuracy of thepin 16 and tolerances of holes 18 and 20.

FIG. 2 shows a typical erosion of the braze joint interface of amodified gun barrel gas cylinder attachment. Gun barrel 24 has a gasopening 26 which is in alignment with vertical gas opening 28 andlongitudinal gas opening 30 of gas cylinder 32. The gas cylinder isattached by means of a brazed joint 34 which also has a gas opening 36therein. It is noted that the gas orifice 38 of the firing systemcomprises the opening 26 in the gun barrel, opening 36 in the brazedjoint, and vertical opening 28 of the gas cylinder.

In FIG. 2, the hatched portion 34a of the brazed joint is the originalbrazing and the unhatched portion 34b illustrates the portion of thebrazed joint which has been eroded away.

FIG. 3 shows a currently-used method to alleviate the problemillustrated in FIG. 2. In this FIGURE, gun barrel 40 and gas cylinder 42have step-drill holes 44 and 46 respectively. A solid, cylindrical pin48 is inserted in the larger diameter portions of the step-drill holesto locate the gas cylinder 42 on the barrel 40 and then brazed in place.The gas orifice passage 50 is axially drilled through locating pin 48after brazing is complete. It is noted that the braze at either end ofthe pin can and will be eroded in time but the area for the gas to acton is small, and limited to the end ring area of the pin. (See referencenumeral 52 in FIG. 3.) Therefore, the finite maximum separative forcecan easily be estimated and allowed for in the design of the brazejoint. This predictable design is obviously preferable to the unlinedorifice hole where braze erosion and resultant loss in joint strengthwill proceed at an unknown rate.

However, this method (i.e. FIG. 3) requires the postbraze drilling ofthe orifice hole 50 which must then be externally sealed. This isaccomplished by threading an outer length 50a of the hole, inserting asteel ball 54, holding the sealing ball in place with a hollow-hex headset screw 56, and staking the set screw to prevent loosening. As can beexpected, the method of sealing the gas orifice opening is expensive.

The present invention is shown in FIGS. 4-8. FIG. 4 shows an exaggeratedview of a gun barrel 58 gas cylinder 60 assembly incorporating aspirally-wound spring locating pin 62. Spring pin 62 comprises a hollowspring steel pin and is used to locate the gas cylinder 60 on the barrel58 for the brazing operation, acting between the larger diameter portionof the step-drill holes 64 and 66 in both the barrel and gas cylinder.Step-drill holes 64 and 66, when aligned, comprise the orifice hole 68.The joint is fluxed, assembled and preform-brazed in the normal manner.No additional machining or drilling of the orifice hole 68 or sealingthe orifice hole with a separate ball and set screw is necessary ordesirable. In addition to this economy, the tendency of a hollow springpin to expand in diameter, until confined, means that the clearancesthat normally would exist between a solid pin and orifice holes areabsorbed by this expansion in each hole, thus improving the locationaccuracy of the joint. See FIG. 4.

In summary, the use of a spring pin as the locating pin not only retainsthe advantages of the solid, drilledthrough pin in preventing brazeinterface erosion and joint failure and limiting erosion to the smalland predictable ring area at pin end, but it also: (1) improves thelocation accuracy of the gas cylinder due to spring pin expansion, and(2) provides greater economy by eliminating post-braze drilling and theseal ball and set screw.

FIG. shows an exaggerated, schematic view of a spring locating pin 62used to align opening 70 of barrel 72 with opening 74 of gas cylinder 76wherein the enlarged portion 70a of step-drill hole 70 of the barrel hasa greater diameter than the enlarged portion 74a of step-drill hole 74of the gas cylinder. When this happens, the spring pin 62 assumes theposition shown in FIG. 5 and engages the gas cylinder at points A andthe barrel at point B.

FIG. 6 shows an exaggerated, schematic view of a spring locating pin 62used to align opening 78 of barrel 80 with opening 82 of gas cylinder 84wherein the enlarged portion 78a of step-drill hole 78 of the barrel hasa smaller diameter than the enlarged portion 82a of step-drill hole 82of the gas cylinder. In this case, the spring pin 62 assumes theposition shown in greatly exaggerated form in FIG. 6 and engages thebarrel at point C and the gas cylinder at point D.

In either case, i.e. FIG. 5 or FIG. 6, the spring pin 62 is biasedagainst the barrel and gas cylinder walls to accurately locate theopenings and accurately position the gas cylinder on the barrel.

FIG. 7 shows atop view of a simple roll pin 62a which has beensuccessfully used in attaching gas cylinders to model and testbedrifles. However, flux does enter the orifice passage via thelongitudinal slot 84 in the pin 62a and small quantities of gas acted onthe braze interface via this slot.

A preferred, spirally-wound spring locating pin 62b is shown in FIG. 8.Because of the labyrinth form of the pin, the flux is prevented fromentering the orifice passage and the explosive gases are prevented fromcontacting the braze point area on the sides of the elongated pin 62b.

What is claimed is:

l. A firearm having an elongated barrel through which a projectile meansis propelled by explosive propellant gases, an orifice, in said barrelfor bleeding off said explosive gases after the projectile means haspassed the orifice, a gas cylinder positioned adjacent to said barreland having an opening in substantial alignment with said barrel orifice,a hollow spring pin means positioned in and biased outwardly against thebarrel orifice and the gas cylinder opening for accurately locating andaligning the orifice and opening for permitting the explosive gases topass from the barrel through the pin means to the gas cylinder, andmeans securing said hollow spring pin means to said barrel and gascylinder.

2. A firearm as recited in claim I wherein said hollow spring pin meanscomprises a cylindrical length of tubing having a slot running thelength of said tubing and in the same direction as the axis of saidtubing so that the slit tubing is free to move to a smaller diameter forinsertion into said barrel orifice and said gas cylinder opening andthen be spring-biased outwardly against the walls of the barrel orificeand the gas cylinder opening to align said orifice and opening and holdsaid slit tubing in place.

3. A firearm as recited in claim 1 wherein said hollow spring pin meanscomprises an elongated pin having a labyrinth form in which an innerfree end is overlapped by an outer free end, thus permitting the pin tomove inwardly to a smaller diameter and then be biased outwardly whiledefining an enclosed, gas-sealed passageway through which the explosivegases can pass from the barrel to the gas cylinder.

4. A firearm as recited in claim 3 in which said means securing saidhollow spring pin means to said barrel and gas cylinder is a braze jointwhich is effected after the spring-biased pin is in position.

5. In a firearm wherein high-pressure gas produced by propellantcombustion is channeled from the bore of a barrel via a passage to anattached gas cylinder device whereby the gas is allowed to impinge onareas to produce force and motion to the firearm action, the improvementcomprising a hollow locating and aligning pin means positioned in saidpassage and secured to said barrel and to said gas cylinder device, saidpin means comprising an elongated roll-type pin which is spring-biasedagainst the walls of said passage, and means to rigidly secure said pinto said gun barrel and gas cylinder device whereupon the pin acts as aliner for the passage.

6. In a firearm as recited in claim 5 wherein said passage comprisesstep-drill holes in the bottom portion of the barrel and the top portionof the gas cylinder device so that when aligned. the step-drill holeswill constitute a continuous passageway from the inside of the barrel tothe inside of the gas cylinder device. said hollow pin means beingpositioned in and acting between the larger diameter portion of saidstep-drill holes in both the barrel and attached gas cylinder device andbeing spring-biased outwardly so as to accurately locate the step-drillholes and form the gas passageway.

7. In a firearm as recited in claim 6 wherein said means to rigidlysecure said pin to said gun barrel and gas cylinder device comprises abraze joint which is formed after the pin means is inserted and isbiased out wardly to align the step-drill holes.

8. In a firearm as recited in claim 5 wherein said pin means comprises aspirally-wound strip of flexible metal which has one free end thereofoverlapping the other end to provide an enclosed inner opening whichconstitutes the passageway for the high-pressure gas. saidspirally-wound metal strip pin being capable of being constricted to asmaller diameter and inserted into the passage between the barrel andgas cylinder device where upon being released the pin springs outwardlyinto engagement with the walls of the passage to act as a liner for thepassage.

9. A liner for a high-pressure gas orifice connecting a barrel of afirearm and an attached gas cylinder comprising an elongated spring pinwhich is biased outwardly against the walls which define the orifice toaccurately align and locate the orifice in the firearm with the orificein the gas cylinder and to position the cylinder on the barrel.

[0. A liner for a high-pressure gas orifice as recited in claim 9wherein said spring pin comprises a spirallywound pin having an outerportion overlapping an inner portion so as to eliminate any gap throughwhich said high-pressure gas might leak.

1. A firearm having an elongated barrel through which a projectile meansis propelled by explosive propellant gases, an orifice, in said barrelfor bleeding off said explosive gases after the projectile means haspassed the orifice, a gas cylinder positioned adjacent to said barreland having an opening in substantial alignment with said barrel orifice,a hollow spring pin means positioned in and biased outwardly against thebarrel orifice and the gas cylinder opening for accurately locating andaligning the orifice and opening for permitting the explosive gases topass from the barrel through the pin means to the gas cylinder, andmeans securing said hollow spring pin means to said barrel and gascylinder.
 2. A firearm as recited in claim 1 wherein said hollow springpin means comprises a cylindrical length of tubing having a slot runningthe length of said tubing and in the same direction as the axis of saidtubing so that the slit tubing is free to move to a smaller diameter forinsertion into said barrel orifice and said gas cylinder opening andthen be spring-biased outwardly against the walls of the barrel orificeand the gas cylinder opening to align said orifice and opening and holdsaid slit tubing in place.
 3. A firearm as recited in claim 1 whereinsaid hollow spring pin means comprises an elongated pin having alabyrinth form in which an inner free end is overlapped by an outer freeend, thus permitting the pin to move inwardly to a smaller diameter andthen be biased outwardly while defining an enclosed, gas-sealedpassageway through which the explosive gases can pass from the barrel tothe gas cylinder.
 4. A firearm as recited in claim 3 in which said meanssecuring said hollow spring pin means to said barrel and gas cylinder isa braze joint which is effected after the spring-biased pin is inposition.
 5. In a firearm wherein high-pressure gas produced bypropellant combustion is channeled from the bore of a barrel via apassage to an attached gas cylinder device whereby the gas is allowed toimpinge on areas to produce force and motion to the firearm action, theimprovement comprising a hollow locating and aligning pin meanspositioned in said passage and secured to said barrel and to said gascylinder device, said pin means comprising an elongated roll-type pinwhich is spring-biased against the walls of said passage, and means torigidly secure said pin to said gun barrel and gas cylinder devicewhereupon the pin acts as a liner for the passage.
 6. In a firearm asrecited in claim 5 wherein said passage comprises step-drill holes inthe bottom portion of the barrel and the top portion of the gas cylinderdevice so that when aligned, the step-drill holes will constitute acontinuous passageway from the inside of the barrel to the inside of thegas cylinder device, said hollow pin means being positioned in andacting between the larger diameter portion of said step-drill holes inboth the barrel and attached gas cylinder device and being spring-biasedoutwardly so as to accurately locate the step-drill holes and form thegas passageway.
 7. In a firearm as recited in claim 6 wherein said meansto rigidly secure said pin to said gun barrel and gas cylinder devicecomprises a braze joint which is formed after the pin means is insertedand is biased outwardly to align the step-drill holes.
 8. In a firearmas recited in claim 5 wherein said pin means comprises a spirally-woundstrip of flexible metal which has one free end thereof overlapping theother end to provide an enclosed inner opeNing which constitutes thepassageway for the high-pressure gas, said spirally-wound metal strippin being capable of being constricted to a smaller diameter andinserted into the passage between the barrel and gas cylinder devicewhere upon being released the pin springs outwardly into engagement withthe walls of the passage to act as a liner for the passage.
 9. A linerfor a high-pressure gas orifice connecting a barrel of a firearm and anattached gas cylinder comprising an elongated spring pin which is biasedoutwardly against the walls which define the orifice to accurately alignand locate the orifice in the firearm with the orifice in the gascylinder and to position the cylinder on the barrel.
 10. A liner for ahigh-pressure gas orifice as recited in claim 9 wherein said spring pincomprises a spirally-wound pin having an outer portion overlapping aninner portion so as to eliminate any gap through which saidhigh-pressure gas might leak.